For the clarification of the mechanism of the desiliconization reaction of pig iron with MnO containing blast furnace slag under pressurized and coke-coexisting condition, fundamental experiments were performed by the use of a pressurized high frequency furnace. Based on the experimental results, a mathematical simulation model with consideration of the direct reduction reaction as the coupled reaction with the desiliconization reaction was developed and applied to the quantitative evaluation of the desiliconization reaction with MnO and FeO containing slag.
The following knowledge was obtained.
(1) Under the existence of coke, MnO and FeO are partly consumed by the coupled reaction of direct reduction reaction and the desiliconization reaction is restrained.
(2) The increase of pressure, with the presence of coke, results in the indirect enhancement of the desiliconization reaction through the restraint of the direct reduction reaction.
(3) The effect of the charging of manganese ore on the increase of Mn content and the decrease of Si content in pig iron was quantitatively evaluated by an another simulation model for blast furnace hearth.

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The three phase equilibrium between alloy, spinel solid solution and α-alumina in the Fe-Ni-Al-O system has been fully characterized at 1823K as a function of alloy composition using both experimental and computational methods. The oxygen potential was measured using a solid state cell incorporating yttria-doped thoria as the electrolyte and Cr+ Cr₂O₃ as the reference electrode. Oxygen concentration of the alloy was determined by an inert gas fusion technique. The composition of the spinel solid solution, formed at the interface between the alloy and an alumina crucible, was determined by EPMA. The variation of the oxygen concentration and potential and composition of the spinel solid solution with mole fraction of nickel in the alloy have been computed using activities in binary Fe-Ni system, free energies of formation of end member spinels FeO•(1+x)Al₂O₃ and NiO•(1+x)Al₂O₃ and free energies of solution of oxygen in liquid iron and nickel, available in the literature. Activities in the spinel solid solution were computed using a cation distribution model. The variation of the activity coefficient of oxygen with alloy composition in Fe-Ni-O system was calculated using both the quasichemical model of Jacob and Alcock and the Wagner's model, with the correlation of Chiang and Chang. The computed results for the oxygen potential and the composition of the spinel solid solution are in good agreement with the measurements. The measured oxygen concentration lies between the values computed using models of Wagner and Jacob and Alcock. The results of the study indicate that the deoxidation hyper-surface in multicomponent systems can be computed with useful accuracy using data for end member systems and thermodynamic models.

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A mathematical formulation is developed to represent surface deformation and fluid flow phenomena in an electromagnetically-stirred suspension. The constitutive relationships for representing non-Newtonian behavior at high solid loading are deduced from established experimental data. The results show that significant deformation of the surface occurs at high coil current. There is a marked decrease in the fluid velocity once the solid fraction exceeds about 10%. In addition, the velocity varies non-linearly with the current, showing a rapid increase once a certain shear threshold is exceeded.

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The local heat transfer in spray cooling is theoretically and experimentally studied. The theoretical expression of the heat-transfer coefficient is presented. The distribution characteristics of spray, i.e., the number flux and the size and velocity distributions of the droplets at a given location are combined with the single droplet characteristics upon impingement onto hot surface, i.e., the droplet heat-transfer coefficient, he bottom radius changing with time and the retention time of the drop at the surface. On the basis of expression, the local heat-transfer coefficient is evaluated at various locations in a full-cone spray, the distribution characteristics of which are known. Experiments on the spray-cooling rate of hot surface of a small metal specimen indicate both the fundamental validity and the limitation of the theory.

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Muroran Works of Nippon Steel Corp. formerly sized continuously cast slabs at a breakdown mill before transfer to the hot strip mill. Slabs must be continuously cast with such a width as required by the hot strip mill if they are to be sent directly to the hot strip mill without sizing.
When slabs of a given width were continuously cast at a high speed, the width fluctuates greatly at the exit of caster and sometimes exceeds the allowable slab width at the hot strip mill.
Muroran Works developed a constant slab width control model that uses a width changing device to minimize the slab width fluctuation at the continuous caster; a hot slab width meter of the contact type that can level the edge profile of slab to increase the allowable range of slab width at the hot strip mill; and a roughing edger setup model that can make the most of the small capacity of the roughing edger at the hot strip mill.
As a result, it became possible to supply the hot strip mill with slabs directly from the continuous caster when a powerful vertical scalebreaker or sizing mill is not available. The models and instruments developed are described.

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Steels with carbon content from 0.13 to 0.04% were rolled in temperature range 1220 to 750°C and subsequently air cooled. The microstructure as well as mechanical properties were investigated. The grain size in steels is first gradually decreased with lowering rolling temperature, and then it is fastly increased with further lowering of rolling temperature down to ferrite range. The microstructure is the more coarse and heterogeneous the less completed was the interpass recrystallisation of austenite and the more ferrite was present in steel during the rolling. The rolling in ferrite range produces a strong anisotropy in tensile ductility.

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Commercial heats of Cr and Cr-Mo bearing dual phase steels have been hot rolled by keeping roll finish temperature in the range of 850-880°C and varying the coiling temperature between 200 and 570°C. Mechanical test and retained austenite measurement have been carried out on samples collected from different locations of coils (representing different cooling rates between M_s and M_f temperatures) and also on some of the as received samples which have been given selective heat treatment. The reason for wide range of retained austenite (varying between 0-16%) has been given based on the stability criteria of austenite. Effect of retained austenite on mechanical properties has been discussed and a distinct beneficial effect of retained austenite on mechanical properties, particularly elongation has been found.

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The effect of grain-boundary configurations on the creep rupture strength was investigated using austenitic 21Cr-4Ni-9Mn (21-4N) steel in the temperature from 600 to 1000°C. The grain-boundary sliding was also examined on specimens crept at 700°C. Further, discussions were made on the relation between the amount of grain-boundary sliding and the initiation of grain-boundary cracks.
The creep rupture strength was improved by serrated grain boundaries at temperatures above 600°C. The specimens with serrated grain boundaries had longer rupture lives than those with normal straight grain boundaries even at high temperatures around 1000°C.
It was experimentally confirmed that both the life to crack initiation and the life of crack propagation increased by the serrated grain boundary at temperatures around 700°C, and that only the resistance to crack growth of the steel was improved by the strengthening at high temperatures above 900°C.
The average amount of grain-boundary sliding in specimens during creep at 700°C was reduced by serrated grain boundary to about one-third or one fourth of that of the specimen with straight grain-boundary configuration. A good agreement was found between the experimental results on the critical amount of grain-boundary sliding for crack initiation and those predicted by the theory of triple point cracking.

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Tensile deformation behavior at very low temperatures near absolute zero has been investigated mainly for an Fe-42%Ni steel to prove the applicability of the computer simulation method presented previously by the authors and to clarify the effects of several testing conditions on serration. The amount of the elongation accompanied with each load drop in serration increased with increasing deformation rate and also for shorter gage length. Hourglass type specimens also showed a similar serration to the specimens with a smoothed and reduced section. Serration was smaller in liquid He(II) than in liquid He(I). All these characteristics of serration observed experimentally were reproduced with computer simulation. The computer simulation clarified that the high thermal conductivity and diffusivity led to a decreased amount of elongation accompanied with each load drop. The simulation also showed that work hardening played an important role for deformation behavior at very low temperatures. Serration, however, arose by the calculation even in the absent of work hardening, whereas the specimen deformed only at the center in this case. Deformation behavior observed experimentally was discussed in terms of the results obtained by the simulation.

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A cell and some monitor techniques for the content of hydrogen permeated through a 21/4Cr-1Mo steel at high temperatures have been developed by using an electrochemical method. The cell was made of high purity alumina, platinum-coated MgO stabilized zirconia tube (reference electrode), platinum wire (counter electrode) and two alumina tubes (inlet and outlet for argon gas), which were fixed to the cell. Molten NaOH was used as an electrolyte. The hydrogen permeation current obtained at 673K and 0.101MPa hydrogen gas was consistent. The limit of hydrogen detection by this monitoring cell was 0.08ppm. Therefore, the present monitoring cell will be useful for predicting hydrogen attack of steels in operating chemical plants.

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